Dave,
The Johnson keyer circuit was nearly identical across all of their gear, the only differences were in the values of some resistors based upon the B+ and bias voltage levels produced in a specific line of gear. The Valiant preceded the 500 by a couple of months according to the advertisements I have seen and the Valiant keyer is the same across production and is identical in design to that used for the Ranger. My Viking 500 is from 1957 and its schematic shows a 4-400A although the block diagram shows a 4-250 instead.
I have worked on a couple of early 500 transmitters and I don't recall seeing anything different in the keyer circuit. The standard keying circuit shows up at least as early as 1954 in official Johnson literature; the keying modification from Johnson was dated 10-28-54 and this predates the 500 official introduction by over a year.
I wonder if the differences in yours are from modification by a previous owner?
Hi Rodger....thank you for your comments....I always read your stuff.
This is a bit confusing so I'll try to avoid too many words.
It's always a crapshoot buying a used rig....in this case, the changes were documented but I had to dig for them a bit.
The keyer pot had no effect.
The radio keyed ok and seemed to be operating normally on CW.
In looking over the keyer componants I noticed that there were some differences in this unit and the schematic I have.
My manual is different in several ways from the BAMA manual which is a PARTIAL reprint of the earlier manual....note dates on pages.
I assume the earlier manual to be the one that shows the 4-250 in the parts list and on the tube lineup.
I will not confuse the issue any more by mentioning any of the other changes I noticed.....This thread is only about the keyer.
The resistors on the parts list in the new manual shows a change on 3 resistors from the old manual.
OLD NEW
R113 10K R113 4.7K
R114 68K R114 4.7K
R116 33K R116 DELETED
See fig 12 Keyer Wiring in manual.
I used fig 12 in the old manual and the schematic of the new manual to determine the new physical connections.
See pix of the changes and hand scrawled wiring pictorial.
I just tested the rig and it works correctly now.
I should mention that the paper caps C131 & C136 have been replaced with the good stuff.
So....if anyone else is unable to adjust the keyer and is interested enough to dig in there and fix it....this is it.
On my hand drawn pictorial....remove strap from 8>9 if present.
Add insulated strap from 4>8.
The terminal strip is TS115.
The lugs count from left to right.
Dave